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Variation and evolution of sex ratios at the northern range limit of a sexually polymorphic plant.

Abstract

Gender strategies involve three fundamental sex phenotypes - female, male and hermaphrodite. Their frequencies in populations typically define plant sexual systems. Patterns of sex-ratio variation in a geographical context can provide insight into transitions among sexual systems, because environmental gradients differentially influence sex phenotype fitness. Here, we investigate sex-ratio variation in 116 populations of Sagittaria latifolia at the northern range limit in eastern N. America and evaluate mechanisms responsible for the patterns observed. We detected continuous variation in sex phenotype frequencies from monoecy through subdioecy to dioecy. There was a decline in the frequency and flower production of females in northerly populations, whereas hermaphrodite frequencies increased at the range limit, and in small populations. Tests of a model of sex-ratio evolution, using empirical estimates of fitness components, indicated that the relative female and male contribution of males and hermaphrodites to fitness is closer to equilibrium expectations than female frequencies. Plasticity in sex expression and clonality likely contribute to deviations from equilibrium expectations.

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    Pub Type(s)

    JOURNAL ARTICLE

    Language

    ENG

    PubMed ID

    24506681

    Citation

    TY - JOUR T1 - Variation and evolution of sex ratios at the northern range limit of a sexually polymorphic plant. A1 - Yakimowski,S B, AU - Barrett,S C H, Y1 - 2014/2/8/ PY - 2013/10/11/received PY - 2013/12/8/revised PY - 2013/12/16/accepted PY - 2014/2/11/entrez PY - 2014/2/11/pubmed PY - 2014/2/11/medline KW - dioecy KW - gender strategies KW - geographical range limits KW - plant sexual systems KW - sex ratios SP - EP - JF - Journal of evolutionary biology JO - J. Evol. Biol. N2 - Gender strategies involve three fundamental sex phenotypes - female, male and hermaphrodite. Their frequencies in populations typically define plant sexual systems. Patterns of sex-ratio variation in a geographical context can provide insight into transitions among sexual systems, because environmental gradients differentially influence sex phenotype fitness. Here, we investigate sex-ratio variation in 116 populations of Sagittaria latifolia at the northern range limit in eastern N. America and evaluate mechanisms responsible for the patterns observed. We detected continuous variation in sex phenotype frequencies from monoecy through subdioecy to dioecy. There was a decline in the frequency and flower production of females in northerly populations, whereas hermaphrodite frequencies increased at the range limit, and in small populations. Tests of a model of sex-ratio evolution, using empirical estimates of fitness components, indicated that the relative female and male contribution of males and hermaphrodites to fitness is closer to equilibrium expectations than female frequencies. Plasticity in sex expression and clonality likely contribute to deviations from equilibrium expectations. SN - 1420-9101 UR - https://www.unboundmedicine.com/medline/citation/24506681/Variation_and_evolution_of_sex_ratios_at_the_northern_range_limit_of_a_sexually_polymorphic_plant_ L2 - http://dx.doi.org/10.1111/jeb.12322 ER -